Dihydroorotate dehydrogenase (DHODH) inhibitors are compounds useful in the treatment, prevention or suppression of diseases and disorders known to be susceptible to improvement by inhibition of dihydroorotate dehydrogenase, such as autoimmune diseases, immune and inflammatory diseases, destructive bone disorders, malignant neoplastic diseases, angiogenic-related disorders, viral diseases, and infectious diseases.
In view of the physiological effects mediated by inhibition of dihydroorotate dehydrogenase, several DHODH inhibitors have been recently disclosed for the treatment or prevention of the diseases or disorders indicated above. See for example, WO2006/044741; WO2006/022442; WO2006/001961, WO2004/056747, WO2004/056746, WO2003/006425, WO2002/080897 and WO99/45926.
One of the most challenging tasks for formulators in the pharmaceutical industry is incorporating poorly water-soluble drugs into effective pharmaceutical compositions intended for parenteral, e.g. intravenous, or oral administration.
Additionally, the aqueous solubility of poorly water-soluble drugs is an important factor affecting their bioavailability. Improving the solubility of these poorly water-soluble drugs may be achieved using a number of different systems (emulsions, microemulsions, self-emulsifying or micronization). However, all of these systems may need the presence of surfactants to solubilize or emulsify the drugs.
The solubility of poorly water-soluble drugs might also be improved by preparing their addition salts. However, in some cases unstable salts are formed due to hygroscopicity (the process by which a substance attracts moisture from the atmosphere by through either absorption or adsorption) or deliquescence (the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution)
WO2009/021696 discloses 5-cyclopropyl-2-{[2-(2,6-difluorophenyl)pyrimidin-5-yl]amino}benzoic acid and other azabiphenylaminobenzoic acid derivatives as potent DHODH inhibitors. Although this compound has shown adequate pharmacological activity, it is poorly water soluble.
Accordingly, there is a need for water soluble DHODH inhibitors, which are also soluble in the gastrointestinal pH range, and in a physically and chemically stable, non-deliquescent form with acceptable levels of hygroscopicity and relative high melting point. This would allow the material to be further manipulated, e.g. by micronization without significant decomposition, loss of crystallinity or exhibiting any change in polymorphism to prepare pharmaceutical compositions and formulations.